Title

Author

Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Microbiology

Advisor

McNealy, Tamara L.

Committee Member

Henson , J. Michael

Committee Member

Mefford , O. Thompson

Abstract

Microbial biofilms serve as the base of food webs and are important for nutrient cycling in aquatic ecosystems. Nanoparticles (NPs) that enter into these aquatic systems have the potential to settle and become trapped within biofilms. As NPs become further integrated into consumer products, understanding their fate and effects on aquatic ecosystems is of paramount importance. Previous studies from our lab show that gold NPs induce dispersal of Legionella pneumophila biofilms. NPs with platinum and iron oxide core chemistries also lead to similar dispersal events, however, silver core NPs do not seem to induce these events due to NP aggregation. Chemical characteristics of NPs are also important in understanding the impact of NP contamination on trophic interactions. Gold NPs in biofilms altered bacterial interactions with amoebae but similarly-sized, highly stable iron oxide nanoparticles did not have the same impact. In this study we show that NPs become embedded within the extracellular polymeric substance (EPS) matrix of the biofilm. The EPS is composed of proteins, polysaccharides, and extracellular DNA (eDNA). We hypothesize that these NPs are potentially interacting with eDNA within the EPS causing destabilization that leads to biomass dispersal. We found that biofilms treated with DNase yielded a similar dispersion effect as treatment with NPs alone. Subsequent treatment with NPs after DNase (or DNase then NPs) showed no changes to biofilm dispersion after the initial treatment alone. eDNA is only one of several potential binding targets of NPs within the EPS. Future studies will investigate the mechanistic interactions of NPs with specific proteins and bacterial components that may also cause disruptive effects in biofilms.